1. Field of the Invention
The present invention relates to a dielectric resonator antenna mainly used in a microwave or millimeter wave region for a mobile communication, a satellite communication or a satellite broadcasting.
2. Description of the Related Art
Because a mobile communication, a satellite communication or a satellite broadcasting has been rapidly made progress, a transmit-receive device for the communication has been recently used in a house or automobile. In particular, because an antenna representing a radio terminal of the transmit-receive device is set up outside the house or a mobile station, it is required to downsize the antenna because of conditions for a set-up position and external appearance of the antenna.
Therefore, a resonance antenna is conventionally used as a downsized antenna. In the resonance antenna, a dielectric material having a relative dielectric constant higher than one is used to shorten a physical length of the resonance antenna and downsize the resonance antenna. For example, a microstrip antenna and a hemispherical dielectric resonator antenna are well-known. Because the hemispherical dielectric resonator antenna can be made by using a metal mold or the like and the number of etching steps required to make the hemispherical dielectric resonator antenna is small, the hemispherical dielectric resonator antenna can be easily mass-produced.
2.1. Previously Proposed Art:
The hemispherical dielectric resonator antenna is, for example, disclosed in a literature xe2x80x9cTheory and Experiment of a Coaxial Probe Fed Hemispherical Dielectric Resonator Antennaxe2x80x9d IEEE Transactions on Antennas and propagation, Vol.41,No.10, pp.1390-1398, October 1993.
FIG. 1A is an oblique view of a conventional hemispherical dielectric resonator antenna disclosed in the above literature, and FIG. 1B is a cross sectional view of a hemispherical dielectric resonator shown in FIG. 1A.
As shown in FIGS. 1A and 1B, a hemispherical dielectric resonator 301 filled with a dielectric material is disposed on a ground plane 302, a coaxial probe 303 is tightly inserted in the hemispherical dielectric resonator 301 from a rear surface of the resonator 301 through a coaxial aperture 304 to fix the hemispherical dielectric resonator 301 on the ground plane 302. The coaxial probe 303 is located at a displacement b from the center of the hemispherical dielectric resonator 301. When a signal transmitting through the coaxial probe 303 is fed in the hemispherical dielectric resonator 301, the resonator 301 is resonated, and a linearly polarized wave having a fixed frequency is radiated from the resonator 301.
2.2. Problems to be Solved by the Invention:
However, in the conventional hemispherical dielectric resonator antenna, it is required to feed the signal from a rear surface of the resonator 301 to the resonator 301 through the coaxial aperture 304. Therefore, there is a first drawback that it is difficult to arrange the hemispherical dielectric resonator 301 and the coaxial probe 303 on the same plane and a resonance frequency of the conventional hemispherical dielectric resonator antenna cannot be adjusted.
Also, in the conventional hemispherical dielectric resonator antenna, because the coaxial probe 303 is only inserted in the hemispherical dielectric resonator 301 to fix the hemispherical dielectric resonator 301 on the ground plane 302, there is a second drawback that the connection of the resonator 301 and the ground plane 302 is not sufficient and the resonator 301 easily comes off the grand plane 302. Also, because it is difficult to form an array antenna by setting a plurality of hemispherical dielectric resonator antennas in array, the adjustment of antenna characteristics in the array antenna cannot be performed.
Also, in cases where a positional relationship between a mobile body and a base station changes with the passage of time, an optimum antenna angle changes with the passage of time in the linearly polarized wave, and a wave receiving sensitivity is degraded in the conventional hemispherical dielectric resonator antenna. To perform a mobile communication, there is a case that a circularly polarized wave is utilized in the satellite broadcasting or the satellite communication in place of the linearly polarized wave. However, there is a third drawback that the linearly polarized wave is only used in the conventional hemispherical dielectric resonator antenna and the conventional hemispherical dielectric resonator antenna has no operational function for the circularly polarized wave.
A first object of the present invention is to provide, with due consideration to the drawbacks of such a conventional hemispherical dielectric resonator antenna, a dielectric resonator antenna in which a signal feeding line and a dielectric resonator are formed on the same plane and a resonance frequency of the antenna is adjustable.
A second object of the present invention is to provide a dielectric resonator antenna in which a hemispherical dielectric resonator is reliably fixed on a ground plane and an array antenna is easily formed to adjust antenna characteristics.
A third object of the present invention is to provide a dielectric resonator antenna in which a satellite communication, a satellite broadcasting or a mobile communication is performed by using a circularly polarized wave.
The first object is achieved by the provision of a dielectric resonator antenna, comprising:
a metal substrate;
a dielectric resonator arranged on a first side of the metal substrate for radiating an electromagnetic wave according to a signal; and
a dielectric wave-guiding channel connected with the dielectric resonator and placed on the first side of the metal substrate for feeding the signal to the dielectric resonator.
In the above configuration, when a signal is transmitted to the dielectric resonator through the dielectric wave-guiding channel, the dielectric resonator is resonated, and an electromagnetic wave is radiated from the dielectric resonator. Therefore, the dielectric resonator antenna functions as a wave radiation device. In this case, because the dielectric resonator and the dielectric wave-guiding channel are placed on the same side of the metal substrate, the dielectric resonator antenna can be easily set on an antenna base or an automobile.
The first object is also achieved by the provision of a dielectric resonator antenna comprising:
a feeder circuit for feeding a signal;
a metal feeding screw connected with the feeder circuit, a length of the metal feeding screw being adjustable; and
a dielectric resonator, having a screw hole in which the metal feeding screw is fixedly inserted, for resonating an electromagnetic wave at a resonance frequency depending on the length of the metal feeding screw and radiating an electromagnetic wave according to the signal transmitted from the feeder circuit through the metal feeding screw.
In the above configuration, when a signal fed from the feeder circuit is transmitted to the dielectric resonator through the metal feeding screw, the dielectric resonator is resonated at a resonance frequency depending on the length of the metal feeding screw, and an electromagnetic wave according to the signal is radiated from the dielectric resonator. Therefore, the dielectric resonator antenna functions as a wave radiation device. In this case, because the metal feeding screw is tightly inserted in the screw hole of the dielectric resonator, the dielectric resonator is fixedly connected with the feeder circuit. Also, because a length of the metal feeding screw is adjustable, a resonance frequency of the dielectric resonator antenna for the electromagnetic wave depending on the length of the metal feeding screw can be adjusted.
Accordingly, because the dielectric resonator and the metal feeding screw are arranged on the feeder circuit, the dielectric resonator antenna can be easily set on an antenna base or an automobile. Also, because a length of the metal feeding screw is adjustable, the resonance frequency of the dielectric resonator antenna for the electromagnetic wave can be easily adjusted.
The second object is achieved by the provision of a dielectric resonator antenna comprising:
a metal substrate;
a dielectric resonator arranged on the metal substrate;
a signal feeder for feeding a signal in the dielectric resonator to induce an electric field in the dielectric resonator in a one-sided distribution of the electric field; and
fixing means contacting with a rarefactional portion of the dielectric resonator, in which an intensity of the electric field is low, to fix the dielectric resonator to the metal substrate.
In the above configuration, when a signal transmitting through the signal feeder is fed in the dielectric resonator, the dielectric resonator is resonated, an electric field is induced in the dielectric resonator, and an electromagnetic wave is radiated from the dielectric resonator. Therefore, the dielectric resonator antenna functions as a wave radiation device. In this case, the electric field is not uniformly distributed but the intensity of the electric field is one-sided in the dielectric resonator.
Also, a rarefactional portion of the dielectric resonator in which an intensity of the electric field is low is fixed by the fixing means, so that the dielectric resonator is tightly fixed to the metal substrate by the fixing means. To prevent an adverse influence of the fixing means on the electric field, the fixing means is arranged to contact with the rarefactional portion of the dielectric resonator in which the intensity of the electric field is low.
Accordingly, the dielectric resonator can be tightly fixed to the metal substrate by the fixing means while preventing an adverse influence of the fixing means on the electric field.
The second object is also achieved by the provision of a dielectric resonator antenna comprising:
a feeder circuit substrate having a conductive film on its upper surface;
a solid dielectric resonator for radiating an electromagnetic wave according to a signal;
a dielectric film arranged on the upper surface of the feeder circuit substrate to fix the solid dielectric resonator to the feeder circuit substrate;
a microstrip feeding line arranged on a lower surface of the feeder circuit substrate for transmitting the signal to the solid dielectric resonator; and
a signal feeding slot arranged in the conductive film of the feeder circuit substrate and placed just under the solid dielectric resonator.
In the above configuration, a signal transmitting through the microstrip feeding line is fed to the solid dielectric resonator through the signal feeding slot, the solid dielectric resonator is resonated, and an electromagnetic wave is radiated from the solid dielectric resonator. Therefore, the dielectric resonator antenna functions as a wave radiation device. In this case, because the solid dielectric resonator is fixed to the feeder circuit substrate by the dielectric film, the signal transmitting through the microstrip feeding line can be reliably fed to the solid dielectric resonator.
The second object is also achieved by the provision of a dielectric resonator antenna comprising:
a dielectric film;
a patterned circuit arranged on a lower surface of the dielectric film for transmitting a signal;
a conductive substrate arranged on an upper surface of the dielectric film to arrange a signal feeding slot on the upper surface of the dielectric film; and
a solid dielectric resonator arranged on the conductive substrate for radiating an electromagnetic wave according to the signal transmitting through the patterned circuit and the signal feeding slot.
In the above configuration, conductive layers represented by the patterned circuit and the conductive substrate and dielectric layers represented by the dielectric film and the solid dielectric resonator are alternately arranged. In this case, because the adhesive between the conductive and dielectric layers is strong, the solid dielectric resonator and the conductive substrate are tightly connected, and the conductive substrate and the dielectric film are tightly connected. Therefore, the solid dielectric resonator can be tightly fixed to the dielectric film, and the signal can be reliably fed to the solid dielectric resonator.
The third object is achieved by the provision of a dielectric resonator antenna comprising:
a solid dielectric resonator having a first equivalent length for a first electric field induced in a first direction and a second equivalent length for a second electric field induced in a second direction perpendicular to the first direction on condition that the first equivalent length is shorter than the second equivalent length to set a phase difference between the first and second electric fields to an angle of 90 degrees; and
signal feeding means for feeding a signal in the solid dielectric resonator to induce the first and second electric fields.
In the above configuration, when a signal is fed in the solid dielectric resonator by the signal feeding means, a first electric field directed in a first direction is induced in the solid dielectric resonator, and a second electric field directed in a second direction perpendicular to the first direction is induced in the solid dielectric resonator. In this case, because a first equivalent length of the solid dielectric resonator for the first electric field is shorter than a second equivalent length of the solid dielectric resonator for the second electric field, a first phase of the first electric phase differs from a second phase of the second electric phase, and a phase difference between the first and second electric fields becomes an angle of 90 degrees. Therefore, a circularly polarized electromagnetic wave is radiated from the solid dielectric resonator.
Accordingly, the dielectric resonator antenna can function as a radiation device for radiating a circularly polarized electromagnetic wave.